High-speed volume measurement system and method

ABSTRACT

Disclosed is a volume sensor having first, second, and third laser sources emitting first, second, and third laser beams; first, second, and third beam splitters splitting the first, second, and third laser beams into first, second, and third beam pairs; first, second, and third optical assemblies expanding the first, second, and third beam pairs into first, second, and third pairs of parallel beam sheets; fourth, fifth, and sixth optical assemblies focusing the first, second, and third beam sheet pairs into fourth, fifth, and sixth beam pairs; and first, second, and third detector pairs receiving the fourth, fifth, and sixth beam pairs and converting a change in intensity of at least one of the beam pairs resulting from an object passing through at least one of the first, second, and third parallel beam sheets into at least one electrical signal proportional to a three-dimensional representation of the object.

NOTICE OF GOVERNMENT RIGHTS

The United States Government has rights in this application and anyresultant patents claiming priority to this application pursuant tocontract DE-AC12-00SN39357 between the United States Department ofEnergy and Bechtel Marine Propulsion Corporation Knolls Atomic PowerLaboratory.

TECHNOLOGICAL FIELD

This present subject matter relates to systems and methods of high-speedvolume measurement.

BACKGROUND

Existing object sizing technologies include dynamic light scattering,laser light diffraction, mechanical sieves, video imaging, imageanalysis, and scanning light beam projection. The technologies arelimited to analyzing groups of objects, without providing detailedinformation on dimensions or imperfections of individual objects, andhave other limitations as well. These technologies are limited tocreating two-dimensional object signatures or object cross sections,with no ability to do three-dimensional (3D) sizing analysis. Manytimes, the measured object is stationary with the beam scanning theobject multiple times in order to obtain a size measurement. Some ofthese measuring techniques, for example, use only a single light sheetor beam. A single light sheet or beam apparatus allows for only a singlevariable, however, which is insufficient for calculating velocity. Suchan apparatus can detect the presence of an object when the light isshadowed, but has no way of calculating the object size without knowingthe object velocity. Thus a single light sheet or beam is unable todetermine object velocity, requiring that object velocity be known inadvance or input into the measurement device. This is problematic, asobject velocity often varies or is unknown, such as with freely fallingobjects.

For analyzing large numbers of objects or a steady feed, video imagingand image analysis technologies are employed, but are speed-limitedbecause of limitations on processing power available to perform theassociated computer computations. Another object measurement methodologyuses scanning light beam projection. Scanning light beam projection isused on single objects in a process line and requires the object to bemoving at a known or predetermined velocity. Scanning light beamprojection also typically uses rotating mirrors, potentially leading toinaccuracies.

There are several apparatuses embodying one or more of these techniques.One such apparatus is disclosed in U.S. Pat. No. 4,659,937. This patentis described as a laser beam focused on a single axis using acombination of cylindrical lenses and a laser-detector pair used todetect defects and measure wire diameter. Another reference (U.S. Pat.No. 6,927,409) is described as disclosing the monitoring of the drawingof wire or metal bar stock using rotary optical sensors to determine aproduct type and to detect product defects. The rotary sensors measurethe part in two dimensions using polar coordinates. The sensor output iscompared to known product standards to determine the presence and typeof product and to detect any defects.

Yet another reference (U.S. Pat. No. 4,917,494) is described asdisclosing a time-of-flight optical system that uses two closely spacedand substantially parallel light beams for measuring particle sizes byrecording the time-of-flight between the two beams. Each light beam hasa thin elongated cross-sectional shape and the particles are passedthrough the apparatus in a vacuum stream. Another reference (U.S. Pat.No. 5,164,995) is described as disclosing an apparatus for measuringparts on a process line. The parts typically move on a planar trackbetween an optical emitter and a detector pair, with compensations forvoltage variations due to any variation in vertical motion.

Other examples are disclosed in three references (U.S. Pat. Nos.5,383,021; 5,568,263; and 6,285,034), described as disclosing anon-contact multi-sensor bolt-sizing apparatus in which bolts move alonga track, partially blocking laser beams to create shadows oncorresponding detectors. The disclosed apparatuses are described asusing sheets of laser light, both parallel and perpendicular, to producetwo-dimensional part images. These apparatuses are unable to detect apart's velocity, however, unless the part size is known in advance orobtained from evaluating part profile information. Additionally, theparts must also be directed in a desired orientation on a track in orderto be measured. None of these references disclose a way to measure partsin three dimensions moving at an unknown velocity. They are limited totwo-dimensional object signatures or two-dimensional object crosssections.

SUMMARY

Disclosed is a system and apparatus of non-contact volume measurement.In certain exemplary embodiments, the sensor includes first, second, andthird laser sources configured to emit first, second, and third laserbeams; first, second, and third beam splitters configured to split thefirst, second, and third laser beams into first, second, and third beampairs; first, second, and third optical assemblies configured to expandthe first, second, and third beam pairs into first, second, and thirdpairs of parallel beam sheets; fourth, fifth, and sixth opticalassemblies configured to focus the first, second, and third parallelbeam sheet pairs into fourth, fifth, and sixth beam pairs; and first,second, and third detector pairs configured to receive the fourth,fifth, and sixth beam pairs and convert a change in intensity of atleast one of the fourth, fifth, and sixth beam pairs resulting from anobject passing through at least one of the first, second, and thirdparallel beam sheets into at least one electrical signal proportional toa three-dimensional representation of the object.

An exemplary method of non-contact volume measurement includes the stepsof emitting first, second, and third laser beams; splitting the first,second, and third laser beams into first, second, and third beam pairs;expanding the first, second, and third beam pairs into first, second,and third pairs of parallel beam sheets; focusing the first, second, andthird parallel beam sheets into fourth, fifth, and sixth beam pairs; andreceiving the fourth, fifth, and sixth beam pairs and converting achange in intensity of at least one of the fourth, fifth, and sixth beampairs resulting from an object passing through at least one of thefirst, second, and third parallel beam sheets into at least oneelectrical signal proportional to a three-dimensional representation ofthe object.

Certain exemplary methods further include the steps of furthercomprising the step of forming a three-dimensional representation of theobject by converting a plurality of fourth, fifth, and sixth laser beamelectrical signal data proportional to a cross section of the objectinto a spherical coordinate system and interpolating spherical radiibetween the plurality of converted cross-sectional electrical signaldata. Still other exemplary methods include the step of integrating atleast three cross sections together to form a three-dimensionalrepresentation of the object. In certain methods, up to 10,000three-dimensional representations are formed per second. Still otherexemplary methods include the step of calculating a velocity of theobject based on a distance between two parallel beam sheets and a timedelay between when the object passes between a first of the two parallelbeam sheets and when the object passes through a second of the twoparallel beam sheets.

Yet another exemplary method includes the steps of acquiring data on aplurality of light intensities received from three mutually orthogonallight sources; identifying a change in intensity in at least one of theplurality of received light sources; determining a presence of an objectwhen the change in light intensity exceeds a predetermined magnitude ina predetermined number of received light sources; acquiringcross-sectional data points on the detected object; and determining anend of a presence of an object when the change in light intensity fallsbelow the predetermined magnitude in the predetermined number ofreceived light sources. Certain exemplary methods further include thesteps of recording a time that the presence of the object is detected;and recording a time that the presence of the object is no longerdetected.

Still another exemplary embodiment includes a computer program productincluding a non-transitory computer readable medium having storedthereon computer executable instructions that when executed causes thecomputer to perform a method of non-contact volume measurement, themethod including the steps of receiving data on light intensity of atleast one of a first, second, and third laser beams; detecting a changein light intensity in at least one of the first, second, and third laserbeams resulting from an object passing through at least one of a first,second, and third parallel beam sheet pairs; and converting the data onthe change in light intensity of at least one of the first, second, andthird laser beams into an electrical signal proportional to athree-dimensional representation of the object.

BRIEF DESCRIPTION OF THE DRAWINGS

A description of the present subject matter including variousembodiments thereof is presented with reference to the accompanyingdrawings, the description not meaning to be considered limiting in anymatter, wherein:

FIG. 1 illustrates an exemplary three-axis sensor;

FIG. 2 illustrates a single channel of an exemplary sensor;

FIG. 3 illustrates an exemplary sensor optical layout;

FIG. 4A illustrates an exemplary detector signal response;

FIG. 4B illustrates an exemplary calibrated profile;

FIG. 5 illustrates an exemplary beam cross section;

FIG. 6 illustrates an exemplary beam apodization;

FIG. 7 illustrates an exemplary rhomboid prism;

FIG. 8 illustrates an exemplary alternate rhomboid prism;

FIG. 9 illustrates an exemplary sensor system block diagram;

FIG. 10 illustrates an exemplary embodiment of real-time dataprocessing;

FIG. 11 illustrates an exemplary calibration procedure; and

FIG. 12 illustrates a histogram of an exemplary object categorization.

Similar reference numerals and designators in the various figures referto like elements.

DETAILED DESCRIPTION

FIG. 1 illustrates an exemplary three-axis non-contact volume sensor100. The sensor 100 is capable of measuring and/or calculating objectvolumes at rates of up to approximately 10,000 objects per second. Theexemplary embodiment of FIG. 1 is a three-axis sensor, but additionalaxes can be used without departing from the scope of the present subjectmatter.

FIG. 2 discloses an exemplary embodiment of a single channel module of anon-contact volume sensor 100. In the exemplary embodiment shown,measurements are taken on three axes having three beam sheet pairs 19a/19 b. In the exemplary embodiment of FIG. 2, the three beam sheetpairs 19 a/19 b form three measurement planes. Although the embodimenthas three beam sheet pairs 19 a/19 b, only one is shown for clarity.Each beam sheet pair 19 a/19 b has a source 1 and a corresponding pairof detectors 10 and 11, with outputs from the detectors 10 and 11combined to form a three-dimensional profile. In the exemplaryembodiment of FIG. 2, source 1 includes a laser diode and focusing lens.Other lasers, such as HeNe lasers, solid state lasers, or other beamsources known to those of skill in the art may also be used withoutdeparting from the scope of the present subject matter. The beamwavelength in this exemplary example is in the red light range, 600-670nm, but other wavelengths may be used without departing from the scopeof the present subject matter. A violet or ultraviolet laser diode witha wavelength below 410 nm, for example, may be used if a smaller beamfootprint (diameter) or higher measuring resolution is desired. Emittersof still other wavelengths may be used without departing from the scopeof the present subject matter.

Measurements can be taken simultaneously on each axis, but need not be,as the object may pass through the parallel beam sheet pairs atdifferent times depending on the location of the measured object. In theexemplary embodiment of FIG. 2, each beam sheet pair 19 a/19 b isindependent of other beam sheet pairs 19 a/19 b. The use of three axesis exemplary only, as additional axes may be used without departing fromthe scope of the present subject matter. In the embodiment shown in FIG.1, the sensor axes are arranged at rotational angle of 120 degrees toeach other, at an elevation angle of about 35 degrees from thehorizontal plane. These angular offsets and elevations are exemplaryonly. Other values can be used without departing from the scope of thepresent subject matter.

In this exemplary embodiment, an object 16 passes through laser lightsheets 19 a/19 b, with the object 16 creating shadows in the lightsheets 19 a/19 b. These shadows are focused onto detectors 10 and 11,which produce one or more electrical signals proportional to a crosssection of the object 16 as it passes through the light sheets 19 a/19b. In the exemplary embodiment of FIG. 2, source 1 emits beam 2, whichis split by a beam-generator assembly 3 into a first and second parallelbeams 4 and 5. The beam splitter shown polarizes the first and secondparallel beams 4 and 5 in the embodiment shown, but need not in otherexemplary embodiments. The beams 4 and 5 pass through beam expansionlenses 6, an apodizing filter/optical aperture 7, and beam-collimatinglenses 8. Lens generically refers to any optical assembly used by thoseof skill in the art to focus or redirect light. Parallelism is definedby the equationθ=½*sin⁻¹(2*ε/W)

where θ is the angle that two beams or beam sheets point toward eachother, ε is the desired axial measurement accuracy, and W is the objectaperture of the beam 14. For an ε of 0.0001 inches and an objectaperture size W of 0.75 inches, θ is 0.008 degrees.

In exemplary embodiments using non-cylindrically symmetric sources, thesource may also contain a half wave plate 23, which when turned rotatesthe polarization of incident laser beam 2. The laser beam 2 passesthrough a beam-generator assembly 3, creating parallel beam 4, which hasa p-polarization, and parallel beam 5, which has an s-polarization. Theratio in intensities between the two beams is determined by thepolarization of the input beam 2, which is controlled by the half waveplate 23. Alternately, for cylindrically symmetric beams such as HeNelasers or circularized laser diodes, the polarization of the incidentlaser beam may be rotated by rotating the laser source, which eliminatesthe need for a half wave plate.

The output of the beam-collimating lens assembly 8 is a pair of beamsheet sheets 19 a and 19 b spanning the path of object 16. Object 16crosses light sheets 19 a and 19 b at different times, creatingtemporally offset shadows (not shown) on collecting lenses 9, whichfocus the shadowed beams 19 c and 19 d onto detectors 10 and 11. Thedetectors 10 and 11 convert changes in beam intensity resulting fromthese shadows into one or more electrical signals proportional to theobject cross-section and/or a three-dimensional representation of theobject. In certain exemplary embodiments, the light can be focusedthrough a polarizing beam splitter 17 prior to reaching detectors 10 and11. In certain exemplary embodiments, mirrors 12 and 13 may be used tofold the optical path to reduce the size of the measurement apparatus100. Other optical components known to those of skill in the art can beused in place of or in addition to these components. For example, aphased emitter or a wide stripe laser or laser array could be used toproduce the light sheets. Integrating spheres, apertured detectors,band-pass filters, one or more receiver arrays, or other detectionmethods known to those skilled in the art may be used without departingfrom the scope of the present subject matter.

FIG. 3 illustrates an exemplary sensor optical layout. In the exemplarylayout of FIG. 3, a light sheet 19 a is shown in an orthogonal view ofthe exemplary embodiment of FIG. 1. In the embodiment of FIG. 3, beams 4and 5 (as shown in FIG. 2, for example) exit the beam-generator assembly3 as converging beams. A beam-expanding lens assembly 6 causes the beamsto diverge, and a beam-collimating lens assembly 8 collimates theexpanded beams to form light sheets 19 a and 19 b (as shown in FIG. 2,for example). In the exemplary embodiment shown, sheets 19 a and 19 bare configured such that the width of the sheets exceeds the diameter ofan object 16 traveling through the sheets plus the uncertainty of theposition of the object 16 as it travels through sheets 19 a and 19 b. Acollecting lens assembly 9 converges and focuses sheets 19 a and 19 bonto detectors 10 and 11.

FIG. 4A illustrates an exemplary detector signal response. In theexemplary response of FIG. 4A, a time delay τ between the object fallingbetween the two parallel light sheets is equal toτ=(ts _(A) +tos _(A))−(ts _(B) +tOs _(B))

where ts_(A) and ts_(B) are the start time of the of the data sectionsfor first and second data acquisition channels respectively, and tos_(A)and tos_(B) are the object start times, measured from the beginning ofthe respective data sections.

The velocity of object 16 is calculated from the distance between lightsheets 19 a and 19 b and a time delay between the signals on detectorchannels 15 and 16. As the object 16 travels through beam 19 a and 19 b,it causes the intensity of light received at detectors 10, and 11 todecrease, corresponding to a cross-sectional profile of object 16 as itpasses through a beam sheet. The same cross section profile appears forboth detector signal channels 15 and 16, but delayed in time for thesecond detector signal 22 compared to the first detector signal 21. Asthe physical spacing between beams 19 a and 19 b is known, the velocityof the object 16 can be calculated based on the delay between thesignals on channels 15 and 16. The time delay τ is related to thevelocity V of the object traveling through the object aperture 14,according to the equationV=d/[τ*sin(θ)]−aτ/2

where d is the separation between the two beams (as shown, e.g., in FIG.2), a is the acceleration of the object as it travels through the beams,and θ is the angle of beams with respect to the direction of motion ofthe object.

In certain exemplary embodiments, at least a portion of this informationis used to create a calibrated profile, as illustrated in the exemplarycalibrated object profile 40 of FIG. 4B. The velocity of object 16,calculated by object travel time between sheets 19 a and 19 b, is usedto calibrate the time axis to the x-axis, to create the particle crosssection. Measurement accuracies better than 0.1 percent of the sheetspacing are achieved on the calibrated x-axis. Where objects are freelyfalling vertically without air resistance, a is the acceleration due togravity. Since the distance is known, the data obtained is used toconvert the voltage signal to an output on the y-axis as arepresentation of size of the object 16 passing through sheets 19 a and19 b as a function of time.

FIG. 5 is an illustration of an exemplary beam cross section. In thebeam shown in FIG. 5, each of the laser beams has a long axis 57 and ashort axis 58. The minimum short axis 18 beam size across the aperture14 is set by the Gaussian transmission properties of the laser beam,according to the equationω=√{square root over ([W*λ/(π*sin(θ)])}

where ω is the minimum spot size at the edges of the aperture, W is thewidth of the aperture 14, θ is the angle of light sheets with respect tothe aperture, and λ is the wavelength of the laser beam. The long axis57 beam size is set to be larger than the object aperture 14, so thatobjects falling through the beam do not extend beyond the beam edges.The diameter of the object aperture 14 is larger than the objectdiameter plus any uncertainty in the object position. In certainexemplary embodiments, the long axis 57 of the beam has a flat topprofile to minimize variations in the beam intensity along that axis.

FIG. 6 illustrates an exemplary beam apodization. Beam apodization isused in certain exemplary embodiments to create more uniform emittedbeam profiles by reducing variations in emitted beam intensity.Variations in emitted beam intensity are undesirable, as they can resultin variations in detected beam intensity that are unrelated to detectionand/or measurement of object 16. In the example shown in FIG. 6, theprofile of expanded laser beam 61 along the long axis 57 of FIG. 5before the apodizing filter 7 approximates a Gaussian function, with anintensity that approaches zero at the edges of the beam. The Gaussianfunction is defined by the equation I=exp(−2*x²/ω²), where x is thedistance from the center of the laser beam, and ω is the characteristicexpanded spot size on long axis 57.

As shown in FIG. 6, the Gaussian profile of beam 61 has significantintensity variations. To flatten beam 61, apodizing filter 7, which hasvariable transmission across long axis 57 of the beam and a constanttransmission across the short axis 58 of the beam, is used. Theapodizing filter 7 has an aperture (not shown) which cuts the edges beam61 to form apertured beam 62, and an apodizing function characterized byan apodizing filter profile 63, to create apodized beam 64. Theapodizing filter transmission function has a minimum in the middle,increasing to a maximum at the edge of the beam (as shown in elements 21or 22 of FIG. 4A for example). A typical transmission function is givenby the equationsT=exp(2*x ²/ω²−2*x _(a) ²/ω²) if −x _(a) <x<x _(a), andT=0 if x>x _(a) or x<−x _(a)

where x_(a) is a constant equal to the half-width of the apertured beam.After passing through apodizing filter 7, apodized beam 64 has a profileapproximating an optimal flat top profile on the long axis 57.

FIG. 7 illustrates an exemplary view of a rhomboid prism. The exemplaryprism of FIG. 7 is used in an exemplary beam-generator assembly 3. Theexemplary beam-generator assembly shown includes a rhomboid prism 24 anda secondary prism 25. The rhomboid prism 24 includes optical surfaces26-29. The degree of parallelism between surfaces 27 and 28 isdetermined by the desired accuracy ε and aperture size W as previouslydiscussed. The prism can be any optical material which transmits thebeam. One non-limiting example is BK7, but other optical materials maybe used without departing from the scope of the present subject matter.The secondary prism 25 may be of a variety of shapes, such as a triangleor rhomboid. To minimize the number of manufactured components, thesecondary prism 25 is depicted as a rhomboid with identical dimensionsto the rhomboid prism 24, but need not be. In this exemplary embodiment,rhomboid prism 24 and secondary prism 25 are attached together withoptical cement and polished to achieve a uniform output surface for boththe s-polarized beam 5 and p-polarized beam 4. Other attachmentmechanisms and methods known to those of skill in the art may be usedwithout departing from the scope of the present subject matter.

Several surfaces on the prisms of this exemplary embodiment optionallyinclude optical coatings. The first reflecting surface 27 has apolarization-separating coating, which preferably has an extinctionratio (Tp/Ts) of 1,000:1 on the transmitted beams 4 and 5. The secondreflecting surface 28 also has a polarization-separating coating toreflect the s-polarized beam 5 and further attenuate any residualp-polarization light in the beam and achieves an extinction ration(Rs/Rp) better than 1,000:1. These extinction ratios are exemplary only.Other extinction ratios can be used without departing from the scope ofthe present subject matter. The input edge 26 and output edge 29 of therhomboid prism, and the output edge 31 of the secondary prism areanti-reflection coated with a reflection coefficient less than 0.5% tominimize interference of secondary reflected beams with the primarysystem beams (i.e. the beams that are to be measured). The coatingdiscussed here is exemplary only. Other coatings known to those of skillin the art may be used without departing from the scope of the presentsubject matter.

FIG. 8 illustrates an exemplary of an alternate prism design. In thisexemplary embodiment, the prism is used in exemplary beam-generatorassembly 3. In this embodiment, input beam 2 reflects off a reflectivesurface 32 before impinging on polarizing surface 33 and splitting intopolarized beams 4 and 5. The polarizing surface 33 has apolarizing-separating coating which reflects the s-polarized beam 5 andtransmits the p-polarized beam at an extinction ratio (Rs/Rp) exceeding1,000:1. In this exemplary embodiment, the second reflecting surface 28needs only a reflective coating, as Ts for the polarizing surface is lowenough that any light detected from the secondary beam will notinterfere with measurement of the primary beam. In this embodiment,input surface 26 is on the secondary prism 25. The input surface 25 andoutput surfaces 29, 31 have the same anti-reflection coatings describedin other embodiments above.

FIG. 9 illustrates an exemplary system block diagram of the exemplarysensor 100 of FIG. 1. In the embodiment of FIG. 9, the sensor 100includes laser drive inputs 35 for the lasers, and signal inputs 36 forthe detector pairs 10 and 11. In the embodiment shown, the laser drivers37 are in sensor power module 38. The sensor power module 38 containslaser drivers 37, which deliver power to the lasers 1, and power supply40 for a detector board (not shown). In certain embodiments, sensorpower module 38 compensates for variations in beam intensity. At leastone amplified detector signal passes through sensor power module 38. Thedetector pairs 10 and 11 produce electrical current signals, which arein certain embodiments are optionally converted to voltage signals byamplifiers 39 (shown in dashed lines on FIG. 9). The bandwidth amplifier39 must be large enough to resolve the smallest measured object feature,and the gain must be sufficient to deliver a measurable voltage signal.

In certain embodiments, module 38 corrects for variations in laser powerby sampling at least a portion of the transmitted beams to detect anychange in intensity of the transmitted beam 2. Any changes in intensityare compensated for at the detectors 10, 11 so that these changes arenot incorrectly interpreted as an object passing through beam sheets 19a/19 b. In still other exemplary embodiments, power module 38 includes areference detector (not shown) that detects beam amplitude as it istransmitted, so that transmission variations are not counted as beamshadows.

The exemplary embodiment illustrated in FIG. 9 further includes a dataacquisition station 42, implemented here using a computer 50 having ahigh-speed data acquisition board 43 with a plurality of channels, inthis example two per axis. Each channel is measuring a beam pair (see,e.g., 19 c/d of FIG. 2), with one beam of the beam pair measured on onechannel, and the other beam of the beam pair measured on anotherchannel. The computer 50 optionally includes at least one processor (notshown) as a hardware device for executing software stored in anon-transitory computer-readable medium. The processor can be any custommade or commercially available processor, a central processing unit(CPU), an auxiliary processor among several processors associated withcomputer 50, a semiconductor based microprocessor (in the form of amicrochip or chip set, for example), a microcontroller, or generally anydevice for executing software instructions. In certain exemplaryembodiments, the memory can have a distributed architecture, wherevarious components are situated remote from one another. The processoris configured to execute software stored within the memory, tocommunicate data to and from the memory, and to generally controloperations of the computer 50 pursuant to the software. When the systemsand methods described herein are implemented in software, the methodsare stored on any non-transitory computer readable medium for use by orin connection with any computer related system or method. In the contextof this document, a non-transitory computer readable medium is anelectronic, magnetic, optical, or other physical device or means thatcan contain or store a computer program for use by or in connection witha computer related system or method. The software in the non-transitorycomputer-readable medium may include one or more separate programs, andmay be in the form of a source program, executable program (objectcode), script, or any other entity comprising a set of instructions tobe performed.

The exemplary embodiment of FIG. 9 further includes a software interface44 configured to provide user control of the data acquisition process,with a real-time display 45 showing object cross-sections, and postprocessing analysis tools providing 3D representations 46 and volumemeasurements. If a reference detector is used for each laser to makecorrections for laser power variations, additional amplifier channelsand data acquisition channels may be included. These additionalcomponents are not shown.

FIG. 10 illustrates an exemplary embodiment of real-time data processing1000. In the embodiment shown, computer controls 47 are used to initiatedata acquisition in step 1010. Computer controls 47 include but are notlimited to data rate, record length, and/or trigger threshold. In thisembodiment, data is fed by data channels into an acquisition memory (notshown). The software periodically transfers blocks of data from theacquisition memory to computer (not shown) in step 1020. The computer 50analyzes the data, looking for signal changes corresponding to adetected object. In step 1030 a particle (object) is detected andtriggers image capture and is optionally counted in step 1035.Typically, a detected object triggers on a channel when a signal changeexceeds a predetermined deviation from a threshold level. This deviationis user-settable and must be large enough that noise spikes or dustparticles do not trigger detection and/or counting of false objects, butsmall enough to allow detection by a sensor of the smallest desiredobject size. When a detected object triggers on a predetermined numberof data channels, an object is considered detected, and a data sectionis extracted from the data block for each channel. Each data section hasa fixed width t_(w) and a pre-trigger time t_(pt) to insure that thefull width of the object is detected. Since the object is separatelytriggered on each sensor, the time start t_(s) of the data section forthe triggered channel is separately recorded. In certain exemplaryembodiments, the beginning and end of a detected object are detected bya separate algorithm. Each algorithm scans from the beginning of thedata section, looking for the time at which the signal change exceeds apredetermined threshold. To minimize the chance of a false detection, anaveraging or other smoothing filter may be applied to the data. To findthe end of a detected object, an algorithm performs an analysis from theend of the data section, in the reverse direction. If there may be twoor more detected objects in a data section, the “end of objectdetection” algorithm may be changed to start looking at a peak of thesignal, moving in a forward direction. In exemplary embodiments usingfiltered data, when the filtered data falls below the threshold the endof the object is detected.

In step 1040 velocity is calculated and if required a scaling factor isapplied. One example of how velocity is calculated from the time delayis disclosed in the description of the exemplary embodiment of FIG. 2.The horizontal axis of the cross section, measured in the time domain,is converted to linear units from the standard distance equationX=t*V+½a*t2

If the velocity of the object is large enough (V>>a*t for example), theequation simplifies toX=t*V.

This calibration is applied in step 1050 and is used to help calculatevolume and dimensions and to prepare a two-dimensional cross section instep 1055. These two-dimensional cross sections are combined in step1060 to calculate object volume and dimensions to prepare athree-dimensional representation in step 1065. Data is saved in step1070.

FIG. 11 illustrates an exemplary calibration procedure 1100. In theexemplary procedure shown in FIG. 11, data is collected and transferredto a computer 1110. The time it takes for an object to pass through thebeams is calculated 1120. In certain exemplary embodiments, the timeaxis is calibrated by passing precision objects (not shown), through thesensor assembly 100. A precision object is an object of known size andvolume. These objects can be as small as 0.004 inches in diameter, andcan be accurately measured to within 0.0001 inches. In certain exemplaryembodiments these precision objects are used to create an object profilebased on the light level and/or voltage measured at the detectors. Theseprofiles are compared to signals obtained from objects of unknown sizeand shape and used to estimate the size and shape of an unknown object.A delay τ between two signals is calculated 1130 and the temporal delayis converted into distance (inches in this example) as a distance scale.

As an object 16 passes through the light sheets 19 a/19 b it creates ashadow which is detected by detectors 19 a/19 b, which result in areduction in the output voltage of detectors 10 and 11, which iscalibrated in step 1150. The amplitude of the voltage change V_(PEAK) isrelated to the measured diameter of the object φ, and is used tocalculate the calibration constant for the voltage axis k according tothe equationk=φ/V _(PEAK).

In certain embodiments, each detector response is calibratedindependently to allow for variations in beam intensity and detectorresponsivity. This helps improve the accuracy of converting optical orother beam power to electrical current. As even different detectors ofthe same model can output a different current for a detected opticalpower, it is important to compensate for these differences by knowinghow a detector responds to a detected signal. Detectors can becalibrated to produce a consistent output for a given signal fromdetector to detector by knowing how a particular detector responds.(i.e., the relationship between current and optical power can bedifferent for different detector types) and adjusting the detector asneeded to ensure it is calibrated. In certain exemplary embodiments, theconstant is used to calibrate the detector voltage output axis using theequationZ=A*V

where Z is the axis relating detector voltage to a linear objectdimension, and V is detector output voltage, and A is a calibrationdetermined based on how a detector behaves (i.e., its power output for agiven optical input power). These equations are used to convert a crosssection signal in the voltage-time domain to a fully dimensioned crosssection, as summarized in the example shown in FIG. 11. This process isrepeated for two additional axes in step 1160. In the example shown theadditional axes are orthogonal to each other, but they need not be.Other angular orientations can be used without departing from the scopeof the present subject matter.

FIG. 12 illustrates a histogram of an exemplary object profilecategorization. As shown in FIG. 12, measurements were performed ofobjects of different sizes and shapes, with a histogram of the measuredprofiles. In certain embodiments, a three-dimensional profilerepresentation is created from three cross sections by combining thecross sections in a spherical coordinate system and interpolating thespherical radii between measured cross sections. Additional crosssections can be added to increase the accuracy of a three-dimensionalrepresentation of the object. The three-dimensional profile is anapproximation of the actual object based on a mapping of cross sections,and on points between the cross sections an average value between twocross sections is of the cross sections. In still other exemplaryembodiments, three-dimensional representations are created by taking aradial difference between measured points and calculating a geometricmean to estimate the radius in between points and perform a smoothingfunction in the non-mapped areas to create the three-dimensionalrepresentation. Inputs are taken from measurements from three or moresets of parallel beams. Interpolations can be done by any variety ofsmoothing algorithms known to those of skill in the art.

It will be understood that many additional changes in the details,materials, steps and arrangement of parts, which have been hereindescribed and illustrated to explain the nature of the subject matter,may be made by those skilled in the art within the principle and scopeof the invention as expressed in the appended claims.

We claim:
 1. A non-contact volume sensor, comprising: first, second, andthird laser sources configured to emit first, second, and third laserbeams; first, second, and third beam splitters configured to split thefirst, second, and third laser beams into first, second, and third beampairs; first, second, and third optical assemblies configured to expandthe first, second, and third beam pairs into first, second, and thirdpairs of parallel beam sheets; fourth, fifth, and sixth opticalassemblies configured to focus the first, second, and third parallelbeam sheet pairs into fourth, fifth, and sixth beam pairs; and first,second, and third detector pairs configured to receive the fourth,fifth, and sixth beam pairs and convert a change in intensity of atleast one of the fourth, fifth, and sixth beam pairs resulting from anobject passing through at least one of the first, second, and thirdparallel beam sheets into at least one electrical signal proportional toa three-dimensional representation of the object.
 2. The non-contactvolume sensor of claim 1, wherein the first, second, and third pairs ofparallel beam sheets are mutually orthogonal.
 3. The non-contact volumesensor of claim 2, wherein the first, second, and third detector pairsare on first, second, and third axes arranged at a rotational angle of120 degrees to each other.
 4. The non-contact volume sensor of claim 3,wherein at least one of the first, second, and third detector pairs istilted at an angle with respect to a direction of travel of the object.5. The non-contact volume sensor of claim 1, wherein the first, second,and third pairs of parallel beam sheets are parallel to first, second,and third non-orthogonal planes.
 6. The non-contact volume sensor ofclaim 4, wherein the first, second, and third optical assemblies arefurther configured to collimate the first, second, and third pairs ofparallel beam sheets.
 7. The non-contact volume sensor of claim 1,further comprising an aperture configured to pass the object through atleast one of the first, second, and third pairs of parallel beam sheets.8. The non-contact volume sensor of claim 1, wherein the beam splitteris further configured to polarize at least one of the first, second, andthird laser beams.
 9. The non-contact volume sensor of claim 1, whereinat least one of the first, second, and third beam splitters furthercomprises a first prism and a second prism.
 10. The non-contact volumesensor of claim 1, wherein at least one of the first, second, and thirdbeam splitters further comprises a prism having at least two reflectivesurfaces configured such that the parallelism of the light from the beamsplitter is governed by the equation θ=½*sin⁻¹(2*ε/W).
 11. Thenon-contact volume sensor of claim 1, further comprising at least oneintensity apodizing filter having a long beam axis and a short beamaxis, wherein the filter optically connects with at least one of thefirst, second, and third beam splitters, and has a variable transmissionacross the long beam axis and a constant transmission across the shortbeam axis.
 12. The non-contact volume sensor of claim 1, wherein atleast one of the first, second, and third laser sources emits awavelength between 600 and 670 nm.
 13. The non-contact volume sensor ofclaim 1, wherein at least one of the first, second, and third lasersources emits a wavelength below 410 nm.
 14. The non-contact volumesensor of claim 1, wherein at least one of the first, second, and thirdbeam splitters further comprises a half wave plate which when turnedorthogonally rotates a polarization of one of the two beams of the beampair emitted from the at least one beam splitter.
 15. The non-contactvolume sensor of claim 1, wherein at least one of the first, second, andthird laser sources is rotatable.
 16. The non-contact volume sensor ofclaim 1, further comprising a computer configured to integrate aplurality of object cross sections into a three-dimensionalrepresentation of the object.
 17. The non-contact volume sensor of claim1, further comprising at least one reference detector configured tosample at least one of the first, second, and third laser beams andcompare the sampled beam to a known reference.
 18. A method ofnon-contact volume measurement, comprising the steps of: emitting first,second, and third laser beams; splitting the first, second, and thirdlaser beams into first, second, and third beam pairs; expanding thefirst, second, and third beam pairs into first, second, and third pairsof parallel beam sheets; focusing the first, second, and third parallelbeam sheets into fourth, fifth, and sixth beam pairs; and receiving thefourth, fifth, and sixth beam pairs and converting a change in intensityof at least one of the fourth, fifth, and sixth beam pairs resultingfrom an object passing through at least one of the first, second, andthird parallel beam sheets into at least one electrical signalproportional to a three-dimensional representation of the object. 19.The method of claim 18, further comprising the step of forming thefirst, second, and third pairs of parallel beam sheets into threemutually orthogonal planes.
 20. The method of claim 19, furthercomprising the step of receiving light from the fourth, fifth, and sixthbeam pairs at a rotational angle of 120 degrees to each other.
 21. Themethod of claim 20, further comprising the step of receiving inputs fromat least one of the fourth, fifth, and sixth beam pairs at a horizontalangle with respect to a direction of travel of the object such that aplurality of object cross sections having a plurality of non-coincidenttime axes is created.
 22. The method of claim 18, further comprising thestep of forming a three-dimensional representation of the object byconverting a plurality of fourth, fifth, and sixth beam pair electricalsignal data proportional to a cross section of the object into aspherical coordinate system, and interpolating spherical radii betweenthe plurality of converted cross-sectional electrical signal data. 23.The method of claim 18, further comprising the step of integrating atleast three cross sections together to form a three-dimensionalrepresentation of the object.
 24. The method of claim 23, wherein up to10,000 three-dimensional representations are formed per second.
 25. Themethod of claim 18, further comprising the step of calculating avelocity of the object based on a distance between two parallel beamsheets and a time delay between when the object passes between a firstof the two parallel beam sheets and when the object passes through asecond of the two parallel beam sheets.
 26. The method of claim 25,wherein the time delay is calculated according to the equationV=d/[τ*sin(θ)]−aτ/2.
 27. A method of non-contact volume measurement,comprising the steps of: acquiring data on a plurality of lightintensities received from three mutually orthogonal light sources;identifying a change in intensity in at least one of the plurality ofreceived light sources; determining a presence of an object when thechange in light intensity exceeds a predetermined magnitude in apredetermined number of received light sources; acquiringcross-sectional data points on the detected object; and determining anend of a presence of an object when the change in light intensity fallsbelow the predetermined magnitude in the predetermined number ofreceived light sources.
 28. The method of claim 27, further comprisingthe steps of: recording a time that the presence of the object isdetected; and recording a time that the presence of the object is nolonger detected.
 29. A computer program product comprising anon-transitory computer readable medium having stored thereon computerexecutable instructions that when executed causes the computer toperform a method of non-contact volume measurement, the methodcomprising the steps of: receiving data on light intensity of at leastone of a first, second, and third laser beams; detecting a change inlight intensity in at least one of the first, second, and third laserbeams resulting from an object passing through at least one of a first,second, and third parallel beam sheet pairs; and converting the data onthe change in light intensity of at least one of the first, second, andthird laser beams into an electrical signal proportional to athree-dimensional representation of the object.